I really want to see a good Renesis swap for a 7. Think this is possible? or a better question, would it be "easy" to swap. Possibly a 3 rotor n/a renesis swap if they make a 3 rotor renesis. *crosses fingers* I would love to have the smooth, strong output of a renesis.

 

Sure would be nice. There are no plans for a 3-rotor Renesis, unless Mazda is just lying to us, which I hope they are

The swap shouldn't be too hard to pull off. Any swap will require custom work.. at least we know the engine will fit in easily with a little more room to spare. Stock fuel pump and lines can be retained.

 

The 2 rotor renisis swap might be easy on the newer Miata too. Assuming the gear box might be very similar, only bell housing needed to be modified.

To swap to the FD3S... little more power might be nice. May be a bridgeport renisis? 3 rotor renisis? or even turbocharged renisis? hehe

 

I think a bridgeported NA renesis would be a poor engine for a street car. It would make TONES of hp (350+) but there would be no low end punch at all. The current Renesis already doesn't make the most power down low, so I don't think you would want to make it any worse (what a nice torque "curve" though!!!)

I think a renesis -> miata swap would be pretty sweet. Something tells me that the new Miata will be able to come damn close to bolting in a Renesis engine.

 

i did see a artical saying a 3 rotor renesis is under development......... half year ago........ around 350hp i remember.....

 

id like to know what the difference is in the rotors from 13b-rew to RENESIS. if they are interchangeable then a turbocharged RENESIS would be very doable. id love to do that swap.

paul

 

ooohhh oh you guys know what we are up too!!!!!
well thats the rumors going around in our dealership =)
a 2.0l Renesis a Rotor powerd roadster and more could be in store!!!!! and The Return of the RX-7

 

they added a side seal around the oil seals

mike

 

Other than that, weight, and compression is there a difference? I heard rumours that rotors could be interchangeable

 

they look the same, other than that side seal

mike

 

The rotors are the same physical dimensions as the 13B. They are lighter though as previously stated. Compression ratio is listed as 10 to 1 although I have heard rumors that it is less. Mazda has admitted that it was built to handle boost. The edges are also angle cut on the new rotors. The new seal on the side is not a 3rd oil control ring but rather a sealing ring for the combustion chamber. The problem with not using this seal is that when the rotor passes over the exhaust port, without the seal the hot exhaust gasses are directly hitting the outer oil ring which will quickly lead to the rubber seals death from heat. The new seal blocks off the combustion chamber from ever allowing hot exhaust gasses from reaching the rubber seals.

Have fun doing the engine swap. The engine mounts on a 1st gen are on the front cover. They are on the intermediate housing on the 2nd gen. On the 3rd gen they are on the rear housing. On the Renesis they are on the front rotor housing! You'll need to make new mounts. Trust me on this one. That IS where they are! Don't ask me how I know. I could tell you but then I'd have to shoot you

You will probably have to use the Renesis intake manifold as well. A 2nd gen manifold will not fit. There are 2 different styles of manifold on the Renesis engines. The 210 HP version has only 1 throttlebody on it. The 250 HP version has 2 throttlebodies. 1 main one and 1 smaller one dedicated solely to the 6 port system and located above the alternator. Look closely at some of the pictures and you'll see this. The RX-8 is also drive by wire. No throttle cable! New throttlebody is needed during the swap. I would use the single throttlebody intake for a swap or custom build one. However the Renesis has a 3 stage intake manifold and 3 fuel injectors per rotor which is all computer controlled. It also uses the VDI system from the '89-'91 n/a 2nd gens. The physical internal rotating VDI assembly is the exact same part! Luckily there is an electric fan and electric smog pump (if you want to use one) so mounting these is no concern. The easiest thing to do is to not speculate but rather wait and see for sure how hard it will be once the car is out and there is a supply of available engines.

 

rotarygod:

I'm more interested in employing the exhaust ports when I get around to a rebuild (on my FD). How difficult would this be? Block off the peripheral exhaust ports and machine out the front, intermediate, and rear housings? New manifold (for my RX6)?

Emmisions is one reason, but suposedly the side exhaust ports make the exhaust sound better?

BTW, do you know what operating range the electric (ren) airpump works? I need an electric pump solution, and was eventually getting around to buying a LT1/LS1 pump.

thanks!

 

The problem with this is that you would have to have the Renesis rotors since they have the "3rd" oil seal on the rotors which protects the oil control rings from heat. Without this seal you would burn your oil control rings off in possibly a matter of minutes. You could physically cut the ports into the side housings and machine an insert to replace the stock exhaust sleeve which would block them off. You would also have to add alot of material to the front and rear housings to get the thickness for the exhaust runners. The Renesis has the water seal grooves in the rotor housings again as they were back before 1986 unlike all the rotaries since then. This was done to give a little more thickness to the exhaust runner walls for strength. The Renesis also still uses sleeved inserts in the exhaust ports to help with heat in the housings in that region. If you were to cut your own ports you would need to seal off the water jacket somehow. Its going to take some precision welding all the way around the port and runner to do this. Good luck getting a welder into some of those spots! You can't use plastic steel epoxy here like you can on the intake side. Too hot. It will burn off. I believe that if you put enough effort into it you can make some usable side ports but I don't see how to get around the extra seal issue of the rotors. I think any side exhaust port engine that anyone tries to build based on a 13B (other than Mazda) is going to fail quickly because of the lack of that seal. Mazda tried for many years to do side exhaust ports based off of 12A and 13B engines and this was always where the issue was. They actually played around with this setup at the same time they started using side intake ports but couldn't get it to work based on technology at the time. Incidentally it is the same technology used on every rotary up to the Renesis. It took them 30+ years to figure out how to make it better.

I don't know where or when the electric airpump comes on at. It is a Bosch unit. Looks to be the exact same one that BMW uses.

The side exhaust ports don't really sound any different. The motor is VERY quiet! They also have a muffler the size of a beer keg strapped onto the back of that thing. The car sounds like an RX-7 starting up! Definitely a rotary. Still smokes when started!

 

Cool, thanks for the insight!

Daniel

 

wow, that would be nice to use the dual throttlebody set up. why couldnt the linkage be modified on the t-bodies to accept throttle cable? it still has to move and it still has to read throttle position doesnt it? i think that could be done. i do believe that the double throttlebody set up would prove to be difficult to make work with an aftermarket ecu though. . . knowing the way it works anyways. you wouldnt be able to just hook up a dual throttle cable to them. that 6-port t-body would have to be electronically operated. . . or actuated like the 6th ports are on a 2nd gen.

the mounting does seem to be a problem for an fd or maybe even an fc. that would totally need a new subframe. theres no way you could move that thing back far enough to fit right.

whats really funny is that the 20b now seems more "do-able " than this new 13b!!! hahahaha!!!

paul

 

You know what would be really cool, is if the larger displacement Renesis for the new RX-7 (probably 1.5L) came with a 4-port induction system instead of the 6-port with actuators, and utilised a large single throttle body.

 

Guys I don't think the swap will be easy or cheap. At Seven Stock 2002 the Mazda engineers stated that they wanted to bring the latest version on the FD out with the Renesis engine, but it mounts too high for the body and they tried mounting it in the engine bay several different ways and it just wouldn't work. The only thing I can say is good luck.

 

cars have had dual throttle setups before there was efi

mike

 

You could theoretically actuate the second throttlebody with a vacuum actuator to open it under load in a similar principle to how the 2nd gens turn the auxillary port sleeves but the computer wouldn't know how to compensate for this since it is only judging how far open the primary throttle plate is. Since those runners are completely independent of the others there would be alot more air entering but the computer wouldn't know it. The way to do it, and this could be done on the 2nd gen engines as well, is to use individual runners such as the Renesis but have a single throttle plate for the auxillary ports after the primary throttlebody. This way it could be actuated and still be controlled by the computer. The Renesis computer controls the engine by mass air unlike the speed density system of the 3rd gen or the afm system of the 2nd gens. The intake tract splits off to each throttleplate after the mass air flow sensor. This might work also with the afm of the 2nd gen but why waste the effort when that restictive box is still there.

 

I'm told the way it can be done is to replace the front cover with a 12A one it bolts in nicely. Oh yea, you'll have to switch to a first gen too.

 

The is the mother of all thread revival. I don't have an rx-7 at the moment near me but I was thinking that a 1st gen with a renesis will be an awesome car. I think a custom manifold with ITB would make more sense.

I just found this thread by searching the web. I donknow if anyone has done it already

 

it's been done a few times that i am aware of. search the Gen I forum and you should get a few useful threads - however, i don't recall seeing any threads that detail the swap like there are for 13B-T swap threads.

 

You can't BP a renesis becasue of the coolant passages beneath. Also I beg to differ the multi side port has great torque, the variable intake manifold helps this too. However good torque for a rotary is still Honder pretty low numbers. You can't expect much torque from something that has a 1.1" stroke.

 

only partially true ... i think you may be confusing something. there would be an issue trying to put a bridge on the exhaust ports, but there are a handful of people that have run or are currently running bridgeported Renesis engines. i don't know if any of those guys are on this board or not though.

i can't say any have reported HUGE gains over streetported Renesis engines, but from what i've seen with the Renesis, that's not really all that shocking. the bridges are usually very small.

 

Swap complete!